Armature-core



(No Model.)

G. F. PACKARD.

ARMATURE GORE.

INVENTOR WITNESSES ATTORNEYS AN DREW EJSRANAM. PHOTU-LITMOWASHINGTON. D C

UNITED STATES PATENT ()FFICE.

GRANVILLE F. PACKARD, OF FORT TAYNE, INDIANA.

ARMATURE-CORE.

SPECIFICATION forming part of Letters Patent N 0. 557,869, dated April '7, 1896. Application filed December 26, 1895 Serial No. 573,247. (Nomodeh) To aZZ whom it may c0ncern:

Be it known that I, GRANVILLE F. PAcK- ARD, a citizen of the United States, residing at Fort lVayne, in the county of Allen, in the State of Indiana, have invented certain new and useful Improvements in Armature-Cores; and I do hereby declare that the following is a full, clear, and exact description of the invention, which will enable others skilled in the art to which it appertains to make and use the same, reference being had to the accompanying drawings, which form part of this specilication.

My invention relates to improvements in the construction of laminated cores for electrical induction apparatus which is subject to rapidlyvarying magnetic polarization, and is specially designed for the armature-cores of dynamo-electric generators and motors.

It is well known that while the use of annular blanks or punchings for laminated armatures obviates the necessity of fastening or spider bolts within the body of the core, with their attendant difficulties, as eachlamina when thus constructed is adapted to resist in itself the centrifugal force, yet this construction is too expensive to be practicable for large armatures, because of the great and unavoidable waste of material and the excessively large dies required. Since, then, all very large armatures must be made of segmental punchings, spider-bolts, which pass through the laminae and are embraced more or less within the body of the core or in immediate proximity thereto, may be employed. As the insulation of the said bolts, which thus bind together the said punchings in the core to prevent the generation of local or periodic currents therein, soon disintegratcs when in use, and thus allows the core to become loose, it follows that some construction and arrangement of the said punchings whereby the generation of local currents in said bolts can be obviated without the necessity for insulatin the same is a desideratum.

The object, therefore, of my invention is to provide an improved laminated core of simple and economical construction having such an arrangement of the fastenin g-bolts relatively to the body of the core that the induction of local or periodic currents therein is avoided without the necessity for insulation.

The novel feature of my invention consists in the improved construction of the segmental punchings whereby the spider-bolts, although arranged within the core, are yet so isolated from the body of the core as to be effectually shielded from the magnetic flux of the armature.

In the accompanying drawings, in which spondin g parts throughout the several views, Figure 1 is a plan of one of the sheet-metal punchings, showing the arrangement of the apertured ears in which the fastening-bolts are arranged, and are thereby isolated from the body of the core by a narrow neck or isthmus. Figs. 2, 3, at, 5, 6, and 9 are fragmentary views of the same, showing modified forms of the bolt-securing ears. Fig. '7 is an end elevation of an armature-core constructed in accordance with my invention, the spider ring being broken away in part to show one of the said ears. Fig. 8 is a longitudinal central section of the armature-core and spider.

My improved armature-core 1 is formed or built up of the laminze or punchings 2 of sheet iron, whose outer perimeter may be serrated or notched, as in Fig. 1, orit may be void of projections, as in the fragmentary forms shown, where they are designed for the construction of a smooth-wound armature.

Each lamina or blank constitutes a segment of the complete ring forming the core and may be any desired division thereof.

Each blank or punching in my improved construction is provided upon its inner edge with two or more apertured 'ears 6, '7, 9, 10, 11, or 12, arranged at a proper distance from the ends thereof and connected to the body of the punching by a narrow neck which is vsusceptible of an infinite variety of modifications without departing from the spirit of my invention, as seen in the fragmentary views of the drawings. The said ears in each instance are arranged without the path of the magnetic flux of the core, though integral with the body of the punching. lVhen these punchings are built up in the core 1, by a proper breaking of joints, in a well-understood manner, they are secured in position by a series of fastening-bolts 4;, the number of which corresponds to the number of the ears in the complete punching,

similar figures of reference indicate corre which bolts pass through the said ears and also through the opposite supporting heads or rings of the spider and are secured therein by proper holding-nuts in the usual manner. The fastening-bolts are thus arranged at one side of. and isolated from the path of the magnetic lines of force, which otherwise would tend to encircle the bolts and generate local currents therein, and thus render insulation of the same necessary. The said fastening-bolts can be still more effectively protected from the magnetic flux of the core by a slight radial slit in the said ears, preferably at a point thereon diametrically opposite the contracted neck thereof, as seen in Fig. 9. In this last-described modification the amount of flux embraced by the said bolts is practically reduced to zero. I have thus by my construction of the said ears, particularly that form shown in Fig. 9, practically eliminated all appreciable loss due to induced electrical currents in the bolts by arranging the said bolts outside of the magnetic circuit.

The method by which I have eliminated the local current in the bolts and the operation of my improved core are substantially as follows: As I arrange the car through which passes the fastening-bolt at the extremity of a narrow neck or isthmus the neck is made so narrow that between its opposite sides the difference of magnetic potential is very slight. By varying both thecross-section and the radial length of the said neck I obtain any desired reluctance of the magnetic path surrounding the bolt. Since by the well-known law the magnetic flux I the magneto-motive force of the circuit, (divided by the reluctance of the circuit,) bya proper design of the said ear and isthmus, as above described, I make the ma 'n 'o-m tiv for quotient arism g from i1it 0 e reluctance (practically) 0.

Since the amount of energy dissipated in the fastening-bolts is proportional to the square of the number of lines of force embraced by the said bolts, it is desirable to reduce to the lowest possible limit the amount of flux linked by the said bolts, and to this end I provide a narrowslit in said car, as seen in Fig. 9, which may be employed with equal efficiency in any of the other forms of cars shown in the drawings, thereby securing an almost absolute elimination of the local-current loss in the armature-bolts.

The strength of the contracted neck or isthmus of the said ears must of course be sufficient to resist the centrifugal force to prevent distortion of the core by displacement or bulging of the laminae.

Having thus described my invention and mode of employing the same, what I desire to secure by Letters Patent is- 1. A sheet-iron lamina or punching for an armature-core, consisting of a segment of the core having upon its inner side apertured ears for the fastening-bolts, the said ears havin g their annular portions slitted for the purpose specified and united to the body of the punching by a contracted neck to isolate the said bolts from the magnetic flux of the core, substantially as described.

2. A sheet-iron lamina or punching for an armature-core comprising a segment of the core provided upon its inner and concave edge with apertured ears for the fasteningbolts, and united to the body of the blank or lamina by a contracted neck to shield the said bolts from the magnetic flux of the core, as and for the purpose described.

A laminated core for electrical apparatus built up of segmental laminae having apertured ears for the fastening bolts, and united to the body of the blank by a contracted neck, adapted to shield the said bolts from the magnetic flux of the core, as and for the purpose specified.

4. A lamin ated core for electrical apparatus built up of segmental punchings having apertured ears for the fastening-bolts, the said ears having their annular portions slitted for the purpose specified and united to the body of the punching by a contracted neck to isolate the said bolts from the magnetic flux of the core, all substantially as described.

5. In an armature, the combination with a spider and a series of parallel fastening-bolts, of the laminated core built up of segmental punchings having upon their inner side ap ertured ears for the said bolts, the said ears having the annular portions slitted for the purpose specified and united to the body of the punching by a contracted neck to isolate the said bolts from the magnetic flux of the core, substantially as described.

Signed by me, at Fort lVayne, Allen county, State of Indiana, this 15th day of November, A. D. 1895.

GRANVILLE F. PACKARD.

\Vitnesses:

JAMEs II. POWER, FLAVIUS J. YOUNG. 

